Airblast injectors for multipoint injection and methods of assembly

ABSTRACT

A method of assembling an airblast injector includes forming a fluid passage on an internal conical surface of a first nozzle component and/or on an outer conical surface of a second nozzle component configured and adapted to mate with the first nozzle component to form at least a portion of a fluid circuit therebetween. The fluid passage is configured and adapted to provide passage for fluid in the fluid circuit between the first and second nozzle components. The method also includes joining the first and second nozzle components together by engaging the second nozzle component within the first nozzle component.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/555,363 filed Nov. 3, 2011 which is incorporated by referenceherein in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under contract numberNNC11CA15C awarded by NASA. The government has certain rights in theinvention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to airblast injection nozzles, and moreparticularly, to systems and methods for assembling components ofairblast injection nozzles for multipoint injection.

2. Description of Related Art

Multipoint lean direct injection (LDI) for gas turbine engines is wellknown in the art. Multipoint refers to the use of a large number ofsmall airblast injector nozzles to introduce the fuel and air into thecombustor. By using many very small airblast injector nozzles there is areduction of the flow to individual nozzles, therein reducing thediameter of the nozzle. The volume of recirculation zone downstream ofthe nozzle is thought to be a controlling parameter for the quantity ofNO_(x) produced in a typical combustor. If the recirculation volume isproportional to the cube of the diameter of the mixer, and if the NO_(X)produced is proportional to the recirculation volume, and the fuel flowis taken to be proportional to the square of the diameter of the mixer,then a larger nozzle will produce greater fuel flow, but also a greateremission index of NO_(X) (EINO_(X)).

In addition, conventional construction of small sized injectors,nozzles, atomizers and the like, includes components bonding togetherwith braze. The components have milled slots or drilled holes to controlthe flow of fuel and prepare the fuel for atomization. The componentsare typically nested within one another and form a narrow diametric gapwhich is filled with a braze alloy. The braze alloy is applied as abraze paste, wire ring, or as a thin sheet shim on the external surfacesor within pockets inside the assembly. The assembly is then heated andthe braze alloy melts and flows into the narrow diametric gap andsecurely bonds the components together upon cooling.

Such conventional methods and systems generally have been consideredsatisfactory for their intended purpose. However, when using traditionalbrazing techniques, the braze alloy must flow from a ring or pocket tothe braze area. In doing so, it is prone to flow imprecisely whenmelted. It is also not uncommon for braze fillets to be formed on or incertain features. In some instances intricate or narrow passages canbecome plugged if too much braze is used. These fillets and plugs cannegatively affect nozzle performance. There is higher chance filletformation of and plugs as the nozzle components become smaller, as inmultipoint applications. The difficulties in controlling braze flowemploying traditional brazing techniques is a limiting factor in thedesign of fuel and air flow passages. That is, the shape and size of thepassages is limited by the ability to control the flow of braze.

There remains a need in the art for a method and system of assemblingnozzles that will eliminate or greatly reduce fillet formation and/orplugging and allow for formation of intricate internal fuel and air flowpassages. There also remains a need in the art for such a method andsystem that are easy and inexpensive to make and use. The presentinvention provides a solution for these problems.

SUMMARY OF THE INVENTION

The subject invention is directed to a new and useful method ofassembling an airblast injector. The method includes forming a fluidpassage on an internal conical surface of a first nozzle componentand/or on an outer conical surface of a second nozzle componentconfigured and adapted to mate with the first nozzle component to format least a portion of a fluid circuit therebetween. The fluid passage isconfigured and adapted to provide passage for fluid in the fluid circuitbetween the first and second nozzle components. The method furtherincludes joining the first and second nozzle components together byengaging the second nozzle component within the first nozzle component.

The step of joining can include engaging the second nozzle componentinto the first nozzle component in an interference fit. It is alsopossible for the step of forming a fluid passage to include forming athread around at least a portion the internal conical surface of thefirst nozzle component and/or the outer conical surface of the secondnozzle component. In addition, the step of forming a fluid passage caninclude forming a multiple-start thread around at least a portion of theinternal conical surface of the first nozzle component and/or the outerconical surface of the second nozzle component for providing multipleindividual outlets for the fluid circuit. It is also possible for themethod to include a step of applying braze directly to the jointlocation on at least one of the first and second nozzle components. Themethod can also include a step of applying heat to the braze to form abraze joint at the joint location. The method can also include a step ofwelding the first and second nozzle components together at the jointlocation to form a weld joint.

The invention also provides an injector comprising a fuel distributorwith a fluid inlet, and a fluid outlet. A fluid circuit is provided forfluid communication between the fluid inlet and the fluid outlet andincludes a passage defined along a cone.

The fuel distributor can include an outer distributor ring and an innerdistributor ring mounted within the outer distributor ring. The fluidcircuit can be formed between the inner and outer distributor rings. Itis possible for the outer distributor ring to include an internalconical surface with a helically threaded fluid passage defined therein.The fluid circuit can be defined between the helically threaded fluidpassage of the internal conical surface of the outer distributor ringand an outer conical surface of the inner distributor ring. The internalconical surface of the outer distributor ring can include amultiple-start helically threaded fluid passage defined therein, whereinthe fluid circuit is defined between the multiple-start helicallythreaded fluid passage of the internal conical surface of the outerdistributor ring and an outer conical surface of the inner distributorring.

The fuel distributor can also include a braze or a weld joint mountingthe inner and outer distributor rings together. The braze or weld jointbounds the fluid circuit for confining fluid flowing therethrough.

The invention also provides an injector for use in a multipoint fuelinjection system. The injector includes first and second nozzlecomponents, assembled as described above, to form a fuel distributor.The injector includes an inner heat shield mounted inboard of the secondnozzle component for thermal isolation of fuel in the fuel distributorfrom compressor discharge air inboard of the inner heat shield. Theinjector further includes a core air swirler mounted inboard of theinner heat shield for swirling compressor discharge air inboard of thefuel distributor for atomizing fuel issued from the fuel distributor. Inaddition, the injector includes an outer heat shield assembly mountedoutboard of the first nozzle component for thermal isolation of fuel inthe fuel distributor from compressor discharge air outboard of the fueldistributor.

The outer heat shield assembly can define an outer air circuitconfigured and adapted to issue compressor discharge air outboard offuel issued from the fuel distributor. The outer air circuit can beconfigured and adapted to issue a swirl-free flow of air therethrough.It is also contemplated that, the outer air circuit can be configuredand adapted to issue a converging flow of air therethrough to enhanceswirl imparted on a flow of compressor discharge air issued from thecore air swirler.

These and other features of the systems and methods of the subjectinvention will become more readily apparent to those skilled in the artfrom the following detailed description of the preferred embodimentstaken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject inventionappertains will readily understand how to make and use the devices andmethods of the subject invention without undue experimentation,preferred embodiments thereof will be described in detail herein belowwith reference to certain figures, wherein:

FIG. 1 is a perspective view of an exemplary embodiment of an airblastinjector constructed in accordance with the present invention;

FIG. 2 is an exploded perspective view of the airblast injector of FIG.1, showing how the fuel distributor constructed in accordance with thepresent invention can be assembled;

FIG. 3 is a cross-sectional side elevation view of the airblast injectorof FIG. 1, showing components of the fuel distributor mounted togetherat a braze joint; and

FIG. 4 is an enlarged cross-section side elevation view of a portion ofthe airblast injector of FIG. 1, showing a fluid circuit between aninternal conical surface of an outer distributor ring and an outerconical surface of an inner distributor ring.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings wherein like referencenumerals identify similar structural features or aspects of the subjectinvention. For purposes of explanation and illustration, and notlimitation, a partial view of an exemplary embodiment of the airblastinjectors for multipoint injection in accordance with the invention isshown in FIG. 1 and is designated generally by reference character 100.Other embodiments of the airblast injectors for multipoint injection inaccordance with the invention, or aspects thereof, are provided in FIGS.2-4, as will be described. Airblast injector is adapted and configuredfor delivering fuel to the combustion chamber of a gas turbine engine.

Nozzles used in conventional multipoint LDI configurations were pressureatomizing air assist nozzles. The conventional pressure atomizing airassist nozzles were generally inexpensive and light weight. In suchconventional LDI configurations, it was found that the air assistnozzles had to be very small in order to allow a very large number ofnozzles, for example nozzles in excess of 1000, in order to achieve thetarget low NO_(x) emissions.

Conventional pressure atomizing air assist nozzle systems generally havebeen considered satisfactory for their intended purpose, however it isdesired to reduce cost, complexity and poor low power operability sincethe fuel had to be divided among so many nozzles. The air blast nozzleapproach is advantageous in multipoint applications because of itsability to mix fuel and air more efficiently, permitting the use oflarger nozzles. Fewer air blast nozzles are required than with thepressure atomizing types while still achieving low NOx. This contravenesthe idea that larger nozzles produce higher NOx emissions index (EINOx).However it was found that continuing to increase the diameter of theconventional air blast nozzles in order to reduce the total number,again caused higher NO_(x) emissions. This means that there is anoptimum size associated with nozzles to reduce emissions and that airblast nozzles have had an advantage over conventional pressure atomizingair assist permitting fewer nozzles.

One source of difficulty associated with conventional air blast nozzlesis the way fuel is distributed. Fuel cannot be exposed to excessiveheat, for example wall temperatures exceeding 400° F., withoutdestabilizing and depositing coke in the channel. Coke can block thechannel and impede nozzle performance of the nozzle. In conventionalpressure atomizing air assist nozzles, as discussed above, fuel emanatesfrom a small centrally located hole. The channels feeding the hole areusually located in a symmetrical, location which is easily insulatedfrom heat. In conventional air blast nozzles, fuel is distributed over alarge diameter near the exit of the nozzle. The fuel feed channels inconventional air blast nozzles tend to be much larger than in theconventional pressure atomizing air assist nozzles and they aregenerally adjacent to substantial hot air channels which heat thenozzle. Keeping the fuel cool in conventional air blast nozzles requiresthe use of substantial amounts of heat shielding which adds to the costand weight. In addition, the necessity of flowing air through the coreof the nozzle requires an asymmetric fuel feed channel be utilized whichadds additional complexity. In general, in order to increase theultimate mixing rate with air at the exit, the spread of fuel flowsegregated from air within the geometry of the conventional air blastnozzle makes the nozzle much more vulnerable to fuel overheating andcoke contamination. It is desired to reduce complexity of manufacture,weight, cost and coke contamination of conventional air blast nozzles.

With reference to FIGS. 1 and 2, the invention provides an injector 100for use in a multipoint fuel injection system. Injector 100 includesfirst and second nozzle components, shown as outer and inner distributorrings 102 and 104, respectively, to form a fuel distributor 106.Injector 100 includes an inner heat shield 108 mounted inboard of innerdistributor ring 104 for thermal isolation of fuel, as shown in FIG. 4,in fuel distributor 106 from compressor discharge air inboard of innerheat shield 108. Injector 100 further includes a core air swirler 109mounted inboard of inner heat shield 108 for swirling compressordischarge air inboard of fuel distributor 106 for atomizing fuel issuedfrom fuel distributor 106. In addition, injector 100 includes an outerheat shield assembly 112 mounted outboard of first nozzle component 102for thermal isolation of fuel in fuel distributor 106 from compressordischarge air outboard of fuel distributor 106. Those having skill inthe art will readily appreciate that the spherical shape of outer heatshield assembly 112 allows injector 100 to be rotated to avoid sprayingfluid on adjacent walls while still permitting sealing thereof within acylindrical sealing feature to permit axial travel during thermal growthand contraction of the combustor.

With reference now to FIG. 3, outer heat shield assembly 112 defines anouter air circuit 114 configured and adapted to issue compressordischarge air outboard of fuel issued from fuel distributor 106. Outerair circuit 114 is configured and adapted to issue a swirl-free flow ofair therethrough. Since outer air circuit 114 converges toward thecentral axis, outer air circuit 114 issues a converging flow of airtherethrough to enhance swirl imparted on a flow of compressor dischargeair issued from core air swirler 109.

With reference now FIGS. 3 and 4, fuel distributor 106 includes a fluidinlet 116, and fluid outlet 118, and a fluid circuit 120. Fluid circuit120 is for fluid communication between fluid inlet 116 and fluid outlet118 and includes a three-start helically threaded fluid passage 128,defined along a cone, i.e. internal conical surface 125 of outerdistributor ring 102. Fluid circuit 120 is defined between three-starthelically threaded fluid passage 128 of internal conical surface 125 ofouter distributor ring 102 and an outer conical surface 127 of innerdistributor ring 104. Although shown and described herein as athree-start helically threaded fluid passage, those skilled in the artwill readily appreciate that the passage can be any suitable number ofstarts for a given application. Typically, it is contemplated that onestart should be provided for every 1-inch (2.54 cm) or circumference ofthe passage, however, any other suitable spacing can be used withoutdeparting from the spirit and scope of the invention. Those having skillin the art will readily appreciate that the multiple-start thread andmultiple individual outlets provide enhanced performance when operatingat low pressure, for example, the multiple-starts and multiple outletsof thread allow for even fuel distribution.

In addition, the circumferential distribution of the fuel was aided bythe use multiple-start threaded passages 128 because their inherent flowresistance divided very small quantities of fuel uniformly between fluidcircuit 120. Therein, the velocity of the fuel through fluid circuit 120was substantially higher than it would be in a conventional airblastnozzle without threads 132. High velocity and fluid friction increasefuel cooling ability and helps to keep the metallic walls temperatureadjacent to threads 132 cool without overheating the fuel. Therefore,permitting the multiple-start threaded passages 128 maintain anextremely small wetted surface area of the nozzle as compared toconventional airblast nozzles. The smaller the wetted surface of thenozzle, the less coke contamination occurs. In addition, the use of themultiple-start threaded passage along a conical surface, i.e. internalconical surface 125 and/or outer conical surface 127, reduces theprofile of wetted components and thus permits more space for air throughthe interior of the nozzle.

Further, the geometry of the multiple-start threaded passages 128inherently imparts high degrees of swirl to the exiting fuel. The fuelflows nearly circumferentially at the exit 118 of the threads 132 andforms a uniform film on a short downstream lip of the nozzle. Intenselyco-swirling air helps distribute the fuel circumferentially while itprogresses to the final exit. Those having skill in the art wouldreadily appreciate that the fuel film helps keep the short filming lipcool as it intervenes between the lip and the hot core air.

Now referring to FIG. 4, fuel distributor 106 also includes a brazejoint 130 mounting together inner and outer distributor rings, 104 and102. Braze joint 130 bounds fluid circuit 120 for confining fluidflowing therethrough. Since distributor 106 includes multiple-starthelically threaded fluid passages 128, braze joint 130 bounds fluidcircuit 120 for confining fluid flowing therethrough.

With reference now to FIG. 2, a method of assembling an airblastinjector, i.e. injector 100, is described. The method includes forming afluid passage, i.e. multiple start helically threaded fluid passage 128,on an at least one of an internal conical surface, i.e. internal conicalsurface 125, of a first nozzle component, i.e. outer distributor ring102, and an outer conical surface, i.e. outer conical surface 127, of asecond nozzle component, i.e. inner distributor ring 104. While shownherein in the exemplary context of fluid passage 128 formed on internalconical surface 125 of outer distributor ring 102, those skilled in theart will readily appreciate that fluid passage 128, e.g. including amultiple-start thread as described above, in addition or instead, can beformed on outer conical surface 127 of inner distributor ring 104. Theinner distributor ring is configured and adapted to mate with the outerdistributor ring to form at least a portion of a fluid circuit, i.e.fluid circuit 120, therebetween. The fluid passage is configured andadapted to provide passage for fluid in the fluid circuit between theouter and inner distributor rings.

With continued reference to FIG. 2, the method further includes joiningthe outer and inner distributor rings together by engaging the innerdistributor ring within first the nozzle component. Joining inner andouter distributor rings together also includes engaging the innerdistributor ring into the outer distributor ring in an interference fit.The inner distributor ring can be engaged in an interference fit withthe outer distributor ring by forcefully pulling the inner distributorring towards the outlet of the outer distributor ring. Those skilled inthe art will readily appreciate that due to the conical surfacesinvolved joining the outer and inner distributor rings together, aninterference fit is not required, for example, the inner distributorring can be disposed within the outer distributor ring and fixed with aweld or braze at joint 130. Those skilled in the art will readilyappreciate that without the inner and outer rings joined together in aninterference fit, fuel will still follow the helically threaded fluidpassage 128 due to the pressure differential between the inlet 116 andoutlet 118. In addition, those having skill in the art will readilyappreciate that due to the conical surfaces involved joining the outerand inner distributor rings together does not require thermal resizingto tightly fit the inner distributor ring over the threads to seal thefuel, thereby permitting more efficient and cost effective manufactureand assembly.

With reference now to FIGS. 2 and 3, inner distributor ring can beemployed to form the inner wetted surface. It can be easily slid intoposition from the upstream end of the nozzle. The threads are cut on anadjacent conical surface, i.e. internal conical surface 125 of outerdistributor ring 102, which provides a stop for the inner distributorring. Once the inner distributor ring is in position, it can be tackedinto place at a joint location, i.e. joint location 130, while pressingagainst the threads. The upstream end at the joint location is thenbrazed or welded to keep the ring in position and to seal the fluidcircuit. Those having skill in the art will readily appreciate that thispermits a purely mechanical placement.

In addition, those having skill in the art will appreciate that becausethe inner distributor ring is so short, it minimizes weight it iseffectively cooled by fuel. Reducing or minimizing the wetted surface ofthe nozzle reduces the length of the heat shield, i.e. inner or outerheat shields 108 and 112, respectively, required to keep the wettedsurface carrying components cool. It can also be appreciated that theheat shielding was functionally integrated into the components ofinjector 100. Inner heat shield 108 forms the shroud for inner airswirler 109 into which swirler 109 could be brazed or welded. It alsoforms the inside of the heat shield for the feed tube of fuel circuit120.

In reference to FIGS. 1 and 2, outer heat shield 112 can form the innerair shroud for outer air circuit 114. Both inner and outer heat shields,108 and 112, can be configured to attach together at the back ofinjector 100 where an air sealing weld or braze could be located. Onceattached, the heat shields, 108 and 112, thermally encapsulate inner andouter distributor rings 104 and 102, allowing them to remain at aroundfuel temperature even if the air is at a much higher temperature as itarrives from the compressor. Gaps between adjacent shells permit the hotcomponents to grow radially and axially unimpeded by the coldcomponents. Zones where hot air can touch the fuel conveying componentsare reduced to an absolute minimum. By keeping injector 100 componentssmall, the heat shielding is kept at a reduced weight as compared toconventional injectors. Combining functionality of heat shields 108 and112 keep cost of the components to a minimum.

Now with reference to FIG. 3, the method also includes applying brazedirectly to the joint location on at least one of the outer and innerdistributor rings. The braze is applied over tack beads between theouter and inner distributor rings at the braze location, i.e. brazejoint 130. Heat is then applied to the braze to form a braze joint atthe joint location. Those having skill in the art will readilyappreciate that by applying braze directly to the braze joint, there isless chance for the braze to form fillets on or in certain features, forexample, the fluid circuit.

While shown and described in the exemplary context of multipointinjection for gas turbine engines, those skilled in the art will readilyappreciate that the apparatus and method described herein can be usedfor any other suitable application. Moreover, while the apparatus isshown in the exemplary process described herein, those skilled in theart will readily appreciate that it can be made by any other suitableprocess or processes without departing from the scope of the invention.

The methods and systems of the present invention, as described above andshown in the drawings, provide for systems and methods for assemblingcomponents of airblast injection nozzles for multipoint injection withsuperior properties including reduced formation of fillets and plugsduring brazing. While the apparatus and methods of the subject inventionhave been shown and described with reference to preferred embodiments,those skilled in the art will readily appreciate that changes and/ormodifications may be made thereto without departing from the spirit andscope of the subject invention.

What is claimed is:
 1. A method of assembling an airblast injectorcomprising: forming a fluid passage on an at least one of: an internalconical surface of a first nozzle component, and an outer conicalsurface of a second nozzle component configured and adapted to mate withthe first nozzle component to form at least a portion of a fluid circuittherebetween, wherein the fluid passage is configured and adapted toprovide passage for fluid in the fluid circuit between the first andsecond nozzle components; and joining the first and second nozzlecomponents together by engaging the second nozzle component within thefirst nozzle component.
 2. A method of assembling an airblast injectoras recited in claim 1, wherein the step of joining includes engaging thesecond nozzle component into the first nozzle component in aninterference fit.
 3. A method of assembling an airblast injector asrecited in claim 1, wherein the step of forming a fluid passage includesforming a thread around at least a portion of one of the internalconical surface of the first nozzle component and the outer conicalsurface of the second nozzle component.
 4. A method of assembling anairblast injector as recited in claim 1, wherein the step of forming afluid passage includes forming a multiple-start thread around at least aportion of one of the internal conical surface of the first nozzlecomponent and the outer conical surface of the second nozzle componentfor providing multiple individual outlets for the fluid circuit.
 5. Amethod of assembling an airblast injector as recited in claim 1, whereinthe step of forming a fluid passage includes forming a thread around atleast a portion of the internal conical surface of the first nozzlecomponent.
 6. A method of assembling an airblast injector as recited inclaim 1, wherein the step of forming a fluid passage includes forming amultiple-start thread around the internal conical surface of the firstnozzle component for providing multiple individual outlets for the fluidcircuit.
 7. A method of assembling an airblast injector as recited inclaim 1, further comprising: applying braze directly to the jointlocation on at least one of the first and second nozzle components; andapplying heat to the braze to form a braze joint at the joint location.8. A method of assembling an airblast injector as recited in claim 1,further comprising: welding the first and second nozzle componentstogether at the joint location to form a weld joint.
 9. An injectorcomprising: a fuel distributor with a fluid inlet, and fluid outlet, anda fluid circuit for fluid communication between the fluid inlet and thefluid outlet, wherein the fluid circuit includes a passage defined alonga cone.
 10. An injector as recited in claim 9, wherein the fueldistributor includes an outer distributor ring and an inner distributorring mounted within the outer distributor ring, wherein the fluidcircuit is formed between the inner and outer distributor rings.
 11. Aninjector as recited in claim 10, wherein the outer distributor ringincludes an internal conical surface with a helically threaded fluidpassage defined therein, and wherein the fluid circuit is definedbetween the helically threaded fluid passage of the internal conicalsurface of the outer distributor ring and an outer conical surface ofthe inner distributor ring.
 12. An injector as recited in claim 10,further comprising a braze joint mounting the inner and outerdistributor rings together, wherein the braze joint bounds the fluidcircuit for confining fluid flowing therethrough.
 13. An injector asrecited in claim 10, wherein the outer distributor ring includes aninternal conical surface with a multiple-start helically threaded fluidpassage defined therein, and wherein the fluid circuit is definedbetween the multiple-start helically threaded fluid passage of theinternal conical surface of the outer distributor ring and an outerconical surface of the inner distributor ring.
 14. An injector asrecited in claim 10, further comprising a weld joint mounting the innerand outer distributor rings together, wherein the weld joint bounds thefluid circuit for confining fluid flowing therethrough.
 15. An injectorfor use in a multipoint fuel injection system comprising: first andsecond nozzle components assembled as recited in claim 1 to form a fueldistributor; an inner heat shield mounted inboard of the second nozzlecomponent for thermal isolation of fuel in the fuel distributor fromcompressor discharge air inboard of the inner heat shield; a core airswirler mounted inboard of the inner heat shield for swirling compressordischarge air inboard of the fuel distributor for atomizing fuel issuedfrom the fuel distributor; and an outer heat shield assembly mountedoutboard of the first nozzle component for thermal isolation of fuel inthe fuel distributor from compressor discharge air outboard of the fueldistributor.
 16. An injector as recited in claim 15, wherein the outerheat shield assembly defines an outer air circuit configured and adaptedto issue compressor discharge air outboard of fuel issued from the fueldistributor.
 17. An injector as recited in claim 16, wherein the outerair circuit is configured and adapted to issue a swirl-free flow of airtherethrough.
 18. An injector as recited in claim 16, wherein the outerair circuit is configured and adapted to issue a converging flow of airtherethrough to enhance swirl imparted on a flow of compressor dischargeair issued from the core air swirler.